If you want to grind this trophy as fast as possible go into trials mode, any character you feel you can do a ex move with and choose any trial. The trial mode will give you full ex bar. Then just do your ex move (using the three attack buttons. You might want to map that move to a face button if it's easier), wait the 3 seconds it takes to recharge (and for dan to reset otherwise he'll block the attack, and I'm unsure if that will count) and do your ultra move again.